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Orchids at Kew and Wakehurst Place

Most poeple think of orchids as greenhouse plants which require great heat and high humidity to grow and flower well. Others are more familiar with the wild orchids of Britain and Europe, which are mostly small plants with seasonal growth and short flowering seasons during the spring or summer. Both kinds are crown today at Kew and a few native species were already happily established at Wakehurst Place before it became a part of the Royal Botanic Gardens.

Late winter and spring are probably the best times to visit Kew in order to see the widest possible variety, but there are orchids on view throughout the year in the Princess of Wales Conservatory and usually in the Alpine House as well. A careful inspection of the Peat Garden, Rock Garden and adjacent woodland garden will often reveal a few species in leaf and flower. At Wakehurst Place, some naturally occurring orchids in the area known as the Slips have been added to by plants raised from seeds at Kew, and there are additional wild species in the woodlands and nearby Loder Valley Nature Reserve.

 The Princess of Wales Conservatory

The main glasshouse displays of orchids at Kew are staged in the Princess of Wales Conservatory. This building, opened by the Princess of Wales in July 1987, replaced the groups of older style houses, mostly of wood and brick, known as the Ferneries and the The range (orchids had been grown in the latter, both on benches and planted out in beds with other tropical plants, for many years).

The conservatory covers an area of 4490 sq m and brings under one roof the main tropical and subtropical herbaceous collections on public display. The design of the building makes maximum use of the sun's power for heating, and enables rainwater to be collected and stored for watering, as well as making an architectural contribution to Kew's heritage of outstanding glasshouses.

 The tropical plant collections require widely varying environments, so the glasshouse is divided by means of glass walls into 10 climatic zones. The temperature required in each zone is preset and controlled by a central computer which also monitors humidity levels and switches on overhead mist lines if the humidity in any zone falls below a predetermined figure. In the same way, shading in response to direct sunlight, and ventilation when temperatures rise, are controlled automatically. This automation means that there is a rapid response to changes in the house when the sun comes out, or if there is a sudden shower, which is not only good for the plants but also creates great savings in staff time. 

Zones 6 and 7 are adjacent to each other on the western side of the glasshouse and are allocated to tropical and cooler-growing orchids respectively. In order for the orchids to grow in a natural way, it is essential to create the correct balance of temperature and humidity in their environment. In Zone 6 a minimum temperature of 18ºC (64ºF) is maintained at night and a relative humidity of about 95%. During the day the temperature rises gently to 23ºC (73ºF), causing a fall in relative humidity to around 85%. Misting the epiphytic orchids by hand early in the morning offsets this fall in humidity, and in high summer, when ventilators are wide open, an afternoon misting may also be necessary. During the rest of the year the humidity is allowed to fall to about 60% in the afternoon so that the plants are all quite dry before the temperature falls in the evening.

A similar cycle is maintained in Zone 7, where the minimum night temperature is 11ºC (52 ºF) rising to 18 ºC (64ºF) during the day. Neither zone is allowed to become warmer than 30ºC (86ºF). Many of the plants grown in Zone 7 require a cool, dry resting period during the winter and the relative humidity is then reduced. Constant manipulation of the computer controls helps staff to maintain the prescribed conditions in the most efficient way. 

Like the rest of the Princess of Wales Conservatory, Zones 6 and 7 are designed as landscapes in which most of the planting is permanent. This reduces the labour needed to maintain the plants and results in a more natural display for visitors, who may begin to appreciate how epiphytic and terrestrial orchids grow in the wild. Rockwork gives height and shape to the beds and provides suitable planting spaces for those species which normally grow on rocks. The compost mixture used in the beds is made up of two parts of coarse peat to one part each of coarse bark, medium bark, charcoal and hydroleca. It is moisture-retentive while being well drained and well aerated. Large tree ferns in each zone give a look of maturity to the planting by their size, as well as providing shade and a more humid microclimate. 

Trees are needed to display epiphytic orchids effectively and can be provided in three ways. The first is to build artificial trees from pieces of cork oak bark fixed to a concrete or wire framework. Trees made in this way look rather artificial but are very long-lasting. The second method is to use real branches sawn to suitable shape and size and plunged in the beds. Early on in the planning of the orchid zones of the conservatory, it was decided to adopt the second method as it gives a more natural effect. However, under the glasshouse conditions of high temperature and high humidity, wooden branches decay rapidly: Robinia is considered to last the longest, followed by oak, but neither can be expected to last for much longer than three years. For this reason, the advance assembly of 'epiphyte trees' in the nursery is needed to ensure a succession for coming years. 

The third method is to grow orchids on living host trees, but this requires careful longterm planning. Suitable hosts need to be large enough to support the orchids, yet not so vigorous that they outgrow the glasshouse too quickly. Rough bark, which retains a little moisture to encourage orchid roots, is advantageous. In Zone 7 a graceful cycad, Cycas siamensis, supports two dendrobiums from Thailand - D. aphyllum and D. polyanthum. These dendrobiums are deciduous and benefit from a dry rest in winter at a time when the cycad also requires a drier period. A Mexican palm, Brahea calcarea, has a rough hairy trunk and has been planted with Laelia anceps and L. furfuracea. Their roots quickly took advantage of the moisture held there and have penetrated the leaf bases of the palm. In Zone 6 Cyathea crinita from Sri Lanka supports the rapidly growing Coelogyne mayeriana whose roots are quick to probe the scaly trunk of the tree fern. 

Many coelogynes will form large clumps of pseudobulbs in time, and some of these, such as C. pulverula and C. swaniana from West Malesia (South-East Asia), have been established on oak branches in Zone 6. Their pendulous spikes of white or cream flowers with brown markings can be seen hanging below the branches. Their close relative Pholidota imbricata also makes a sizeable clump when grown on a branch. Its erect or arching spikes bear many small white flowers two or three times a year. 

Coelogynes and pholidotas are planted together on branches as they all enjoy well-watered conditions throughout the year. Some tropical epiphytes which require a dry, dormant period in winter are planted in groups where this need can be met. One branch supports three Dendrobium species, all from various parts of Thailand. The two species at the top of the branch are D. aphyllum and D. polyanthum. They are deciduous and flowers develop on the leafless, pendent canes before their new growth begins in spring. D. aphyllum has soft mauve flowers with a white lip, while D. polyanthum has white flowers with a yellow lip. Below them, on the same branch, D. cariniferum has been planted. In the glasshouse this species needs to be kept drier in the winter than summer but not as dry as the preceding two. D. cariniferum is semi-deciduous and in the early spring produces cream flowers suffused with bright orange, with a brighter orange patch on the lip. 

In Zone 7 epiphytes from Mexico such as Lycaste aromatica have been established by attaching them to branches with the base of the plant surrounded by sphagnum moss. This retains enough moisture in the summer to permit the full expansion of the large, fast-growing leaves. In the winter months, after shedding the leaves, the pseudobulbs are allowed to dry out and this ensures successful flowering the following spring. 

Not all the epiphytes in Zone 7 require a dry winter. Many species originating from the cloud forests of central and southern America need to be kept damp and humid even in the cooler months. These have been planted on logs and stumps close to the ground where it is always cooler and more humid, and the curiously shaped flowers of Restrepia guttulata and the blood-red colouring of Masdevallia angulata always surprise visitors who bend down to examine them. 

Some epiphytic orchids have proved to be too large and heavy to be displayed on branches. Dendrobiums in the section Spatulata, the antelope dendrobiums, can form large clumps of canes when mature and have been planted in the ground behind retaining logs. Their roots will eventually grow out over the logs, and this will convey the impression of their epiphytic nature. When mature, the canes of Dendrobium helix easily reach a height of 2 m and bear many spikes of flowers in pastel pinks, greens and yellows, with characteristic, corkscrew-shaped petals. Dendrobium gouldii reaches the same proportions and has yellow-ochre coloured flowers with deep brown twisted petals. 

Some epiphytic orchids are grown in hanging baskets rather than on branches. Ansellia africana is particularly suited to this method of cultivation, as, in addition to its silvery, cane-like pseudobulbs and fresh green leaves, it forms a fascinating cluster of tightly packed, spiky aerial roots around the basket, completely obscuring it from view. The pseudobulbs become weighed down by the heads of yellow flowers spotted with brown during the early spring and their fragrance perfumes the whole glasshouse when the temperature is warm. 

Cultivation and display in hanging baskets is especially suited to species with pendulous flowers, for these can then be examined at eye level. Dracula bella from Colombia is grown in this way in Zone 7. Its flowers open out widely to form a triangle of yellow sepals which are nearly covered with blood-red spots. A long, red tail hangs from the tip of each sepal and the inflated white is lip hinged so that it wobbles in the breeze. 

The Australian lithophytic dendrobiums are grown on rocks behind the pools in Zone 7. Dendrobium speciosum has stubby pseudobulbs and arching sprays of creamy flowers. Dendrobium kingianum has more slender pseudobulbs and leaves and bears dark pinky purple flowers in February. These two species form a hybrid, Dendrobium X delicatum, which is rare in the wild but responds well to cultivation and has pink or white flowers. 

Orchids which would normally grow in the ground are planted in the beds where their terrestrial habit can best be appreciated. In Zone 6, Spiranthes cernua var. odorata which comes from the swamps of Florida, flourishes underneath a tree fern which is given copious amounts of water. The orchid grows luxuriant tufts of shiny foliage and spikes of white flowers throughout the autumn. Phaius tankervilleae also originates from marshy habitats and one of its hybrids grows particularly strongly here. The flower spikes of red and pink flowers grow to a height of 1.5 in and their robust foliage is imposing at any time of the year. Phaius australis var. bernaysii is a slightly smaller species with flower spikes up to 1.2 in tall. The flowers are yellow and white. Between them the three kinds of Phaius produce flowers for eight months of the year: The hybrid Phaius usually begins to flower in October and lasts until February; P. tankervilleae flowers from Christmas until April and P. australis var. bernaysii from March until May.

One of the jewel orchids, so‑named for their beautiful leaves, is Ludisia discolor from Indonesia. The leaves of this species are a velvety‑green tinged with bronze and marked with a delicate network of pink veins. It grows Calanthe sylvatica, a terrestrial orchid that is widespread in shady forests in Africa, and is similar to related species in Asia. Bob Campbell close to the surface of the compost but produces spikes of white flowers about 30 cm high which have a beautiful perfume. The cultivar L. discolor 'Doris Stein' has longer flowers and more vigorous growth but is sadly lacking in scent.

The South American slipper orchids in the genus Phragmipedium give interest over a long period as they are rarely bare of flowers. Phragmipedium longifolium can be seen growing with some of the hybrids of which it is a parent, including P. Sedeni with deep crimson and pink flowers, P. Calurum with pale pink and white flowers veined with green, P. Lemoinerianum with cream flowers veined in red, and P. Ainsworthii with flowers of a soft pink colour veined with green.

Calanthe triplicata and C. sylvatica both have robust evergreen foliage and are planted permanently in the conservatory. Calanthe triplicata has white flowers while those of C. sylvatica are a rich purple. The deciduous calanthes, such as C. vestita C. rubens and the hybrids C. Veitchii and C. Diana Broughton, are plunged in the beds when they flower but cultivated in the nursery for the rest of the year, since their need for a dry, dormant period would be difficult to cater for if they were planted permanently in the moist conservatory beds.

Whilst most of the tropical terrestrial orchids growing in Zone 6 have been found to grow well in a bark-based compost, a small area of loam-based mix seems to be more suitable for the eulophias which are planted in the area linking the African and Asian orchids. Eulophia andamanensis is a species from Thailand which flowers in late spring and produces many spikes 60 cm tall. The delicate, elegant flowers are a muted green and cream. Eulophia guineensis inhabits the African side of the conservatory and has larger pink flowers with a pink and white lip. These two species are both deciduous and their leafless pseudobulbs contrast in winter with some of the evergreen species such as E. petersii. This succulent species is widespread in the dry parts of the Middle East and Africa and has thick leaves which conserve water. Its flower spikes may be as much as 1.5 m tall and bear many small pink and green flowers.

The genus Cymbidium is of outstanding horticultural importance for the large number of man-made hybrids Produced from a few of its 44 species. The tropical species, such as C. aloifolium and C. bicolor, are grown in Zone 6 on a mesh pillar against which their hanging flowers can be properly viewed and appreciated. Those s Species originating from the cooler conditions of higher altitudes are grown in Zone 7. Several species, including C. tracyanum and C. lowianum, are planted at ground level among tree stumps and rocks to show their lithophytic habit. Cymbidium tracyanum flowers in the early winter and fills the area with the pervasive Flagrance of its gingery-striped flowers. Cymbidium lowianum flowers in spring and several colour forms are planted in the conservatory. The typical form is the best known with its long arching sprays of soft green flowers with a deep red marking on each lip. In some plants the red is lacking and plants with a yellow or greenish patch have been known in the past as var. concolor. These plants are now recognised as a distinct cultivar, C. lowianum 'Concolor'. The var. iansonii has a light brown patch on the lip. Genuinely terrestrial cymbidiums, such as C. cyperifolium from Nepal, have been planted closer to the front of the bed, where their relatively small and subtly coloured flowers can be seen. A group of interesting primary hybrids between C. madidum and C. elegans have been established epiphytically on branches. Cymbidiums have large root systems, so in order to get the seedlings established the roots are padded with mineral rock fibre and wrapped around with moss. This ensure that enough moisture is retained around the roots.

In addition to the permanent plantings of orchids there is a small area in both Zone 6 and 7 for more transient displays. These areas, behind glass security screens, are used to display plants in flower which are grown for most of the year in the Reserve Collection of orchids in the Lower Nursery (see chapters 4-8). Displays are changed frequently so that regular visitors can see colourful flowering orchids at any time of the year.

As in any other garden, the orchid display areas in the Princess of Wales Conservatory will change as plantings mature. It is hoped that every visitor will gain enjoyment from the range of form and colour which the orchids in flower demonstrate and will also appreciate something of the way orchids grow in their natural habitats.

The Alpine House and its Surrounds

The new Alpine House at Kew was opened in 1981 and is rather different from the more traditional houses of its kind. Square in outline, it somewhat resembles a pyramid raised on vertical walls above a surrounding moat. Ventilators are operated automatically making it possible for a very high proportion of the roof to be open. The atmosphere in the house is always cool and fresh.

A dominant feature is a large, refrigerated, rectangular bench which is specially managed for arctic and tropical montane plants with great success. The curious South American orchid Altensteinia paleacea can be seen in the tropical montane section of this 'fridge' It bears a slender spike of papery bracts which partially hide the small and rather insignificant white flowers. 

Around the 'fridge', the rest of the house has been landscaped with Sussex sandstone to provide a variety of niches for alpine and cool temperate plants from all over the world. In front of the sandstone are plunge areas where plants grown in pots in the nursery give a continuous procession of flowering material against the backcloth of the more permanent plantings Display benches also provide space for the exhibition of some of the larger pot-grown plants and recent acquisitions. Much of the permanent planting requires conditions that are frost-free, and if it is cold, then dry cold is less damaging than a lot of rain. Thus plants in the Alpine House are kept somewhat dry in winter and, compared with the surrounding area outside, a little warmer in summer.

At the edge of a small pond the soil is permanently moist and one of the finest of the marsh orchids flourishes here. Dactylorhiza foliosa has increased in size tremendously since it was first planted. Its shiny leaves are conspicuous throughout most of the year and it regularly produces more than 20 flowering spikes which last for a month or more in perfection. In the wild, it is known only in Madeira and it is now rare in its native habitat, though single growth plants can still be found. Seedlings from the plant at Kew have been raised in the Micropropagation Unit and are regularly in demand for distribution to other botanic gardens.

On the other side of the Alpine House, a small gully has been prepared for peat-loving plants which like a little more shade. A few temperate orchids from the Pacific region have become established here and flower well. In mid-summer the slender pink spikes of Spiranthes sinensis are conspicuous. In late winter the Japanese dendrobium, Dendrobium moniliforme, loses its leaves, and white or pale pink flowers appear on its upright canes. Nearer the front, a tiny Australian helmet orchid, Corybas diemenicus, has a tiny leaf almost flat on the ground and produces a small dark brown flower, usually in the spring. Other species planted here include one or two Pterostylis species from Australia, the so-called greenhoods, and some of the more tender Japanese calanthes.

Satyrium nepalense is maintained in a pan in the nursery and plunged amongst the rocks for display when the flowers appear. Most years this happens in spring and autumn, with a dry rest period after each flowering. The shell‑pink flowers on tall spikes are a pretty contrast to the pale green leaves that clasp the base of the stem.

Many other temperate orchids are grown behind the scenes in the nursery and put on display in the Alpine House as they come into flower, either on a bench among other plants in pots, or plunged into the moist soil by the pond or the rocky slope by the doors depending on their individual needs. Pans of Pleione species and hybrids are always spectacular and, by careful timing in repotting and bringing into growth each spring, there is a long succession of blooms on view. Terrestrial orchids from Australia, including some of the Diuris species, can be seen regularly. Robust plants of some of the Mediterranean orchids which grow and flower during the winter and spring, are also displayed and then removed to dry off and rest under cover during the summer months. Splendid plants of the tongue orchid, Serapias vomeracea, are always an intriguing sight, while a number of the Ophrys species have fascinating bee‑like flowers. Many species of Cypripedium from China, calanthes, Ponerorchis graminifolia and Cymbidium goeringii from Japan as well as other cool‑growing Asian orchids, may be seen on display in season.

The landscaping around the Alpine House permits growth of additional species which require a hot sunny site or a cool shady one and as a result a number of shade‑loving orchids are becoming established in sheltered places. Some of the spotted orchids 'Dactylorhiza species) have done so well that seedlings have grown up which appear to be hybrids. Epipactis gigantea from North America grows well Here and is also spreading, flowering every year in June. Some Japanese calanthes flower very well when the season is kind, but unfortunately their rather fleshy flower spikes are very susceptible to sudden, late frosts.

In 1980, a peat garden was built nearby in the shade cast by the Jodrell Laboratory. It was a splendid site for cypripediums, but sadly they were all stolen one night. However, Wakehurst Place a number of orchids are still doing well. One of the spotted orchids, Dactylorhiza iberica, from the eastern Mediterranean, spreads by underground rhizomes and has become so prolific that it has to be wee e out where it invades other precious plants. Another spectacular plant in this bed is Dactylorhiza X transiens a natural hybrid rescued, as a small plant, from a building site in Suffolk and sent to Kew in 1979. Good cultivation and hybrid vigour have resulted in the Present specimen, which bore 45 spikes in 1990.

The Rock Garden

The Rock Garden at Kew extends over more than an acre between the Herbaceous Ground and the Princess of Wales Conservatory. Originally excavated from a level site more than a hundred years ago, it has been changed and improved in various ways. The banks of soil are now held in place by large rectangular pieces of Sussex sandstone which resemble outcrops. Streams flow away from several waterfalls, and along their banks the soil is permanently moist. Several species of Dactylorhiza, the marsh and spotted orchids, have become established here, some as chance seedlings while others have been planted. The most conspicuous orchid, however, is a large planting of Epipactis gigantea, the large helleborine from North America. It flowers in June and there are usually a dozen or more gingery brown flowers on each upright leafy stem.

The Woodland Garden

At the southern end of the Rock Garden the alpine plants give way to a Woodland Garden where a selection of deciduous trees provides a canopy of shade over the shrubs and herbaceous plants. A number of orchids have flourished here at various times, though sadly many of them were stolen a few years ago. Plant theft has been a surprising problem over the last ten years and for this reason many orchids that could be planted out are now being grown in pots in greenhouses not open to the public, but occasionally some may be put on display.

Still flourishing, and providing quite a spectacle in July, is a group of the marsh helleborine, Epipactis palustris. Though growing in rather more shade than they usually tolerate in the wild, the plants of this British orchid grow luxuriantly here and flower well. The beige and pinkish brown flowers have a large white lip with a conspicuous yellow crest.

Wakehurst Place

Woods and fields occupy the major part of this property of more than 200 hectares, where a wide variety of native plants grow, including at least six different orchids. The best known parts of the estate contain the exotic plants which do not grow well in Kew, especially rhododendrons and some of the southern hemisphere trees and shrubs. The climate is much more equable than that at Kew, although Wakehurst is less than 40 miles away. The rainfall is higher in amount and the temperatures less extreme. Combined with the moisture-retentive soils, these features provide excellent conditions for the growth of temperate plants from around the world. Plants from China and Japan, as well as other parts of the Himalayan region, are a speciality and include more than a dozen orchids.

Neither the wild nor the introduced orchids are a conspicuous feature at Wakehurst. They have to be searched for during the flowering season, or located with even greater care in spring before they come into flower. The area known as the Slips and adjacent gardens near the stream are good places to look, followed by the woodlands of the Westwood Valley and, with permission, the Loder Valley Nature Reserve.

In April the grass between the magnolia trees at the top of the Slips is still short and a number of wild flowers appear there. Amongst them is the green winged orchid, Orchis morio always one of the earliest of the British orchids to flower. Its short spikes are soon followed, in early May, by those of a much taller cousin. 0. laxiflora. This species has never been recorded in mainland Britain though it is common in suitable damp spots in the Channel Islands. The plants at Wakehurst Place were raised from seeds at Kew under the auspices of the Sainsbury Orchid Conservation Project (see chapter 15). This was one of the first species raised in the laboratory and then transferred from the greenhouse to the open garden, Wakehurst being chosen for the experiment as it was thought to be more suitable than the lawns at Kew. An area where the progress of the plants could be monitored easily was chosen, and within a year of their transplanting, several of the plants flowered. More have matured every year, and other laboratory‑raised plants have been added to the planting. They now make a welcome addition to the garden. Several plants of the spotted orchid, Dactylorhiza fuchsii also grow in this area and flower a little later, though as the grass is longer by then they are less easily seen.

Two species of Epipactis grow wild in the woodlands of the Westwood Valley. These are the broad-leaved helleborine, E. helleborine, which has greenish purple flowers on a tall spike, and the more slender violet or clustered helleborine, E . purpurata, which has purplish flowers. Neither of these is very common. However, the common twayblade Listera ovata, is frequently seen in the woods and dappled shade near the path. With its spikes of yellowish‑green flowers above a pair of basal leaves it is easily recognised. The spotted orchid is also often encountered along the path through Westwood Valley both above and below the Himalayan Glade.

Several Japanese orchids have been introduced to the shaded garden areas between the Slips and the top of Westwood Valley, particularly near the Primula Dell, but they are not yet well established. Calanthes and cypripediums should do well here, provided the winters are not too cold. Gymnadenia conopsea Dactylorhiza aristata and Epipactis thunbergii, all Japanese relatives of familiar European orchids, are also being tried.

Another Asian species, Bletilla striata, has survived for many years in several parts of the gardens, and makes an attractive border plant. The magenta flowers are held above fresh green foliage in early summer. Later, the plant turns brown and the leaves are shed. The pseudobulbs are protected by the soil and mulch from winter frosts.

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